Retorting of oil shale



Sept' 1, 1970 A. l.. sAxToN 3,526,586

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BY QZ'JM/ @wie United States Patent O 3,526,586 RETORTING OF OIL SHALE Arthur L. Saxton, 128 Moun'in Ave.,

Warren, NJ. 07060` Filed Oct. 21, 1966, Ser. No. 588,345 Int. Cl. Clog 1/00 U.S. Cl. 208--11 6 Claims ABSTRACT OF THE DISCLOSURE In a single vessel oil shale retorting operation, the preheating, retorting, combustion and cooling zones are maintained under a pressure within the range of about to about 100 p.s.i.g. and the gas and shale oil mist withdrawn from the retort are washed with af'portion of the already recovered shale oil to improve recovery.

The present invention is directed to a method and apparatus for retorting of oil shale. More particularly, the invention is concerned with retorting crushed oil shale under superatmospheric pressures. In its more specific aspects, the invention is concerned with the maintenance of oil shale under pressure while it is subjected to retorting conditions.

The present invention may be briefly described as a method for retorting oil shale. In the particular method, a single vessel oil shale retorting system lcomprising a preheating zone, a retorting zone, a combustion zone, and a cooling zone is employed. The crushed oil shale is introduced into the preheating zone and tlows serially through said zones and is subjected to preheating, retorting, combustion and cooling conditions as it flows through said zones. During the ow of the oil shale through the zones and subjecting of the oil shale to the several conditions, the zones are maintained under superatmospheric pressure within the range of about 5 to about 100 p.s.i.g. and thereafter the spent shale is discharged from the cooling zone whereby increased capacity of the system is obtained.

The invention also includes apparatus involving a single vessel oil shale retorting system comprising a vertical elongated vessel in which crushed oil shale is introduced into the elongated vessel at its upper end, flows therethrough and is removed from the lower end of the elongated vessel. The elongated vessel is provided with first sealing means at its upper end for introducing the crushed oil shale into the upper end of the elongated vessel and with second sealing means at the lower end of the elongated Vessel for removing spent oil shale from the lower end of the elongated vessel. The first and second sealing means maintain the crushed oil shale under pressure as it ows through the elongated vessel. The first and second sealing means may comprise a lock hopper means provided with pressurizing means and venting means.

The crushed oil shale is suitably pressurized before introduction into the preheating zone and the spent shale is suitably de-pressurized while being discharged from the cooling zone.

The pressures employed in the preheating, retorting, combustion and cooling zones may suitably range from about 5 to about 100 p.s.i.g. although higher pressures may be employed. The optimum pressure for any specic case can be determined by engineering and economic analysis. For most cases, preferred pressures will be within the range from about 40 to about 60p.s.i.g. Ordinarily, there is a pressure drop less than about 5 p.s.i.g. through the several zones.

The shale is suitably introduced into the preheating zone at ambient temperatures which may be in the range from about y0 F. to about 100 F. Temperatures in the preheating zone may range from about 600 F. to about 900 F. with a suitable temperature being about 750 F., the oil shale being preheated by upflowing gas from the retorting zone, the gas being discharged from the preheating zone after preheating with the preheated shale flowing downwardly into the retorting zone.

Temperatures in the retorting zone may range from about 750 F. to about 1000 F.

Temperatures in the combustion zone may range from about 1000 F. up to about 1800 F. although there may lbe localized areas in the combustion zone as high as 2000 F.

Temperatures in the cooling zone may range from about 250 1F. to about 450 F. with the spent shale being cooled to such temperatures. The spent shale may be cooled from a temperature of about 1000 F. to less than 200 F.

In the combustion zone, a free oxygen-containing gas such as air is introduced and the free oXgen-containing gas may be introduced in an amount from about 3,000 to about 6,000 std. cu. ft. per ton of raw shale. A preferred amount may range from about 4,000 to about 5,000 std. cu. ft. per ton of raw shale. The amount of recycle gas which is employed to cool the spent shale in the cooling zone may range from about 12,000 to about 24,000 std. cu. ft. per ton of raw shale. A preferred amount may range from about 12,000 to about 24,000 std. cu. ft. per ton of raw shale. The recycle gas may suitably have a typical composition as follows:

While the foregoing totals to more than 100%, this amount is reflected by the oxygen content which is less than the 0.5 indicated.

The raw oil shale is suitably crushed to a particle size within the range from about 1A" to about 3" at the largest diameter. Smaller sizes than 1A may be used so long as they are not in the form of a dust. The raw oil shale may be fed at a rate from about 1,000 to about 1,500 lbs. per hour per sq. ft. of retort at a pressure of about 40 to about 60 p.s.i.g. The amount of raw shale employed is dependent upon the pressure and will vary accordingly with the pressure employed in the several zones.

The spent shale is suitably withdrawn at a rate of about wt. percent to about 85 ft. percent of the raw shale feed rate.

The sealing means employed in the practice of the present invention at the upper and lower ends of the elongated retorting vessel is suitably a lock hopper sealing means such as known as a Ducon feeder or discharger. Such devices are well known in the industry and are available commercially.

The present invention will be further described by reference to the drawing in which:

FIG. 1 is a ow diagram of a preferred mode and embodiment, and

FIG. 2 is a sectional view of the elongated retorting system of FIG. 1.

Referring now to the drawing in which identical numerals will designate identical parts, and particularly to FIG. l, numeral 1'1 designates a feed belt or similar mechanism in which raw oil shale is dumped into a feed hopper 12. Feed hopper 12 discharges into a lock hopper sealing system 13 which suitably may be a Ducon feeder which is provided with means such as line 14 for venting pressure and means such as line 15 for introducing pressurizing gas.

Feeder 13 connects into a raw shale hopper 16 which feeds shale under pressure by way of lines 17 into an elongated vessel 18 comprised of preheating, retorting, combustion and cooling zones in the order named. The raw oil shale is preheated, retorted, combusted, and cooled in elongated vessel 18 and then is discharged therefrom through a Ducon discharger '19 provided with a vent means such as line 20 for venting pressure. The spent shale discharges onto a moving belt or other system 21 willich transports the spent shale to a refuse dump or the li e.

By virtue of the operation conducted in vessel 18, product gas is withdrawn from the upper end of vessel 18 by line 22 and introduced thereby into a de-mister vessel 23 wherein a separation is made between a liquid phase and a vapor phase, the gases and vapors being withdrawn from vessel 23 by line 24 connected to gas blower 25 and employed as recycle and pressurizing gases which are supplied through blower 25 through line 26K which connects to line 15 and to line 27 which feeds the recycle gas into the lower end of the elongated vessel 18. The amount of gas from blower 25 is regulated by a control valve 28 arranged in line 29 which connects to lines 24 and 26 and is operated through a pressure connection 30.

Air is introduced into the vessel 18 by air Iblower 31 to which air is supplied by line 32, the air under pressure being introduced into vessel 18 by line 33 controlled by valve 34 which is pressure operated.

Recycle line 27 is connected to line 33 by line 35 controlled by valve 36 which is operated through temperature recorder controller 37 connected to the vessel 18. Valve 38 controls the amount of recycle gas introduced into the lower end of vessel 18 being pressure operated.

In de-mister 23, the oil and water are separated from the gases and vapors and are discharged by line 39 into a separator vessel 40 provided with a sump or leg 41 in which water accumulates and which is discharged by line 42. The separator vessel 40 is provided with a screw conveyor 43 which moves the oil and any entrained shale. Line 44, connecting to pump 45, returns the separated oil by way of line 46 to be used in part as wash oil by introducing same lby line 47 controlled by valve 48 into demister 23 by way of branch lines 49 and 50. The other portion of the oil in line 46 may be withdrawn as product by opening valve 51 in line 47. Valve 51 is controlled by liquid level controller I52 on separator drum 40 and is connected by line 53 to valve 51.

Referring now to FIG. 2, the feed hopper 12 connects to the Ducon feeder 13 and is provided with a plurality of chambers 60, 61 and 62. Pressurizing gas may be introduced by line 115 into the feeder 13 which will allow the oil shale under pressure to be discharged into a lower chamber and thereafter the chamber 61 may be vented by line 14. The oil shale under pressure in raw shale hopper 16 then discharges lby pipes 17 through a feed shale distribution device `63 by means of a plurality of feeding tubes y64 into the preheating zone 65 and thence into retorting zone 66, combustion zone 67 into which air is introduced by way of line 33 connecting to air-dilution gas distribution means `68. Thereafter, the retorted oil shale discharges into cooling zone `69 into which recycle gas is introduced by line 27 connecting to a recycle gas pipe distributor 70. A moving grate discharge means 71 introduces the spent shale into discharge means 19 the lower portion of the elongated vessel 18 terminating in a conical section 72 to which means 19 connects. The discharging means 19 is provided with a plurality of chambers 73, 74 and 7S which may be vented by line 20` with the shale dropping onto moving belt 21 as described with respect to FIG. 1.

In the practice of the present invention, a plurality of vessels such as 18 may be employed. Any number may be used but in this example, iive vessels of the nature of vessel 18 are employed.

In a particular operation, 21,460 tons per stream day of oil shale crushed and screened to a 3/s" to 3" size are fed to a battery of the five vessels. The feed oil shale is elevated from ground level, conveyed, and dumped into the feed hoppers associated with each vessel. Oil shale leaves the hopper after about 15 minutes holdup and is charged under pressure to another raw shale hopper which operates at the system pressure. Shale feeding into the pressure system is accomplished with a lock hopper means such as well known in the industry. A suitable device is the Ducon three-door dump gate which is available on the market. The raw oil shale then flows by gravity through a plurality of feeder pipes through a pan-type distribution device located at the top of each retorting vessel. At the bottom of the pan, a plate continuously revolves, permitting shale to flow successively through each of a plurality such as nineteen l-foot diameter feeder pipes that serve to distribute shale at the top of the retort bed. This type of device uniformly distributes the shale over the bed across section, and minimizes diiiculties connected with segregation of the oil shale fines. The oil shale flows by gravity down through the lined retort vessel which may have a diameter of 20 feet. and is contaeted `by an ascending stream of hot gases. After proceeding down through the top 15 feet of the bed, the shale is preheated and retorting has been completed with the shale reaching a temperature of about 1215 F. The retorted shale then enters a 6 feet high combustion zone where the heat necessary to accomplish the retorting is generated. Air is fed to each retort under How control and is distributed across the retort combustion zone by means of six 8-inch slotted distribution pipes. Some of the product gas is introduced to the retort along with the air, thus serving as a diluent and providing means for controlling combustion by controlling the temperature in the immediate vicinity of the distributors to avoid burning the distributors to destruction. Excessively high local temperatures should be avoided because such temperatures cause fusion of shale particles which may plug the retort. The gas may leave the combustion zone at about l500 F., while the oil shale leaves the combustion zone at about 1400 F.

The bottom 14 feet of bed serve as a heat transfer or cooling zone where the descending shale from the combustion zone is cooled by recycle gas to a temperature of 225 F. The recycle product gas is distributed uniformly over each retort by six 12-inch slotted pipes under ow control conditions and is heated to about 1250 F. before entering the combustion zone. Spent shale is discharged from the bottom of the retort through a suitable mechanism such as a moving grate discharge mechanism. This mechanism helps to insure uniform shale ow down through the retort and may be employed to vary the shale discharge rate from the retort vessel. The spent shale is depressurized out of the system with a lock hopper discharge device or means similar to that used for feeding the raw shale into the system. The spent shale may then be conveyed a suitable distance which maybe 200 feet or more from the retort site for waste collection.

The oil product from the retort vessel is condensed in the form of a ne mist by the cool feed shale in the preheating zone of the retort vessel. The product gas containing this mist leaves the top of the retort vessel at about F. and 5l p.s.i.a. The product gas from the ve retort vessels such as employed in this example containing the oil-water mist may be recycled back to the retort vessels in a 60-inch header which feeds into a collection-settling drum for oil recovery. 'Ihe de-mister may suitably be a horizontal vessel about 12 feet in diameter and 40 feet in length which employs sprays, impingement baffle plates, and .entrainment separators to remove the oil and water mist from the gas. Other separation means besides those mentioned may be employed. Recycle product oil serves as a wash material in the de-mister and the mist-free gas leaves the de-rnister at 130 F.. and 51 p.s.i.a. and is separated into a product gas stream which is suitably compressed to 54 p.s.i.a. Part of the compressed gas which may be about 40() MM std. cu. ft. per stream day is recycled back to the retort vessel with 43 MM std. cu. ft. per stream day of diluent gas through a 60-inch header. The liquid oil and water removed from the gas stream by the de-misters flows to a single collection drum with about 15 minutes holdup. Settled water is drained olf the bottom `of the drum at a rate of about 1,365 barrels per stream day. Oil is removed from the drum by liquid level control with 13,800 barrels per stream day being taken as product with 55,000 barrels per stream day being pumped back to the de-mister for use as wash oil.

Very little .entrainment of solids off the top of the retort may be obtained at the superficial gas velocity of 3 feet/second that exists at that point. In any event, solids are removed from the gas stream by the de-mister and the screw conveyor in the drum 40 removes any settled solids with the drained water.

The oil shale employed in the practice of the present invention is suitably the oil shale found in the western states `of the United States. A typical oil shale from Colorado has the following composition:

FISCHER ASSAY Oil, gas/ton 30.0 Moisture plus F.A. water, wt. percent 2.0 Organic CO2, s..c.f./ton 121.0

Organic CO, s.c.f./ton 19.0 Mineral CO2, wt. percent 17.0 Organic material, wt. percent 16.1

Although it is preferred to employ Colorado shale, other shales wherever encountered in the world may be used.

The present invention is quite advantageous and useful in that by virute of employing superatmospheric pressures, the solids mass rate through a given size equipment is substantially increased which allows substantial improvements in processing oil shale while miminizing the cost of the equipment necessary. In the operation decribed in the specific examples, substantial savings and increased rates of oil shale are obtainable. The advantages of the present invention also result from substantial reduction in retorting equipment which is accomplished with eficient process performance. Thus, in the present invention, gas volume is reduced with the increased system pressure employed and this allows increased throughputs and/or reduced size equipment which is substantial. Heretofore, single vessel systems have operated at atmospheric pressure which does not allow the advantages of the invention to be realized. Also, the present invention allows the obtaining of favorable gas/liquid yield ratios and improved product quality.

The nature and objects of the present invention having been completely described and illustrated, and the best mode and embodiment contemplated set forth, what I wish to claim as new and useful and secure by Letters Patent is:

1. In a method employing a single vertical vessel oil shale retorting system comprising a preheating zone, a retorting zone, a combustion zone and a cooling zone in which cool crushed oil shale solids are introduced into said preheating zone and flow downwardly serially through said zones in direct contact with countercurrent gas flow and are subjected to preheating, retorting, combustion and cooling conditions as said solids flow through said zones wherein free oxygen-containing gas introduced into said combustion zone is combusted with retorted solids to form a hot combustion gas which is thereafter directly contacted with preheated oil shale solids in said retorting zone to form a vaporized shale oil product which is withdrawn from said preheating zone as a gas and shale oil mist, said mist having been formed by the contact of the vaporized product with said cool crushed oil shale solids in said preheating zones, the improvement which comprises:

maintaining said zones under a super-atmospheric pressure within the range from about 5 to about 100 pounds per square inch gauge;

washing the gas and shale oil mist with a portion of the shale oil separated from the mist and recovering the other portion of the shale oil;

recovering at least a portion of the gas separated from the mist and introducing said portion of gas into the cooling zone to cool spent shale from said retorting zone;

and discharging spent shale from said cooling zone,

whereby increased capacity of solids mass rate through the system is obtained and gas volume is reduced.

2. A method in accordance with claim 1 in which said crushed oil shale is pressurized before introduction into said preheating zone.

3. A method in accordance with claim 1 in which said spent shale is de-pressurized while discharging same from said cooling zone.

4. A method in accordance with claim 1 in which the pressure on said zones is maintained at about 40 to about pounds per square inch gauge.

5. A method in accordance with claim 1 in which spent shale is discharged from said cooling zone at substantially atmospheric pressure.

6. A method in accordance with claim 3 in which said spent shale is discharged at substantially atmospheric pressure by venting said spent shale during discharge thereof.

References Cited UNITED STATES PATENTS 3,106,521 7/ 1960 Huntington 208--11 3,349,022 6/ 1965 Mitchell et al 208-11 3,384,569 2/1966 Peet 208--11 DELBERT E. GANTZ, Primary Examiner T. H. YOUNG, Assistant Examiner U.S. Cl. X.R. 20L-29, 35 

